Optical beam imaging studies on high power lasers

SLAC National Accelerator Laboratory hosts the unique Linac Coherent Light Source, a free electron x-ray laser (FEL) with high peak brightness, tunability, and narrow bandwidth. Matter in Extreme Conditions (MEC) end station at SLAC investigates the behavior of states in extreme environments of high pressure (several megabars) and temperatures (millions of Kelvin) produced by powerful class 4 lasers using the FEL to probe transient states. Recent experiments in warm dense matter at MEC have required relativistic laser intensities greater than 10$^{\mathrm{19}}$ W/cm$^{\mathrm{2}}$ to create hot electrons. The aim of this study is to characterize the beam spot per pulse to establish high intensity values within 10{\%} accuracy. This will indicate if enough peak intensity has impacted the sample. A numerical code in MATLAB is developed to find spatial and intensity jitter, spot size measurements for four profiles, average peak intensity, and error propagation. This procedure automates previous methods done with imaging software for characterizing beam profile. The implemented code leads to faster and more accurate beam size characterization to eventually enable live pulse-by-pulse measurement, a valuable capability yet to be achieved in laser studies.